Fluid control system



H. GOLD ETAL FLUID CONTROL SYSTEM June 30, 1953 Filed May 24, 1948 Patented June 30, 1953 OFFICE FLUID CONTROL SYSTEM Harold Gold, East Cleveland, and David M. Straight, Cleveland, Ohio Application May 24, 1948, Serial No. 28,959

(Granted under Title 35, U..S. Code (1952),

Claims.

This invention relates generally t0 fluid COR- trol systems and more particularly concerns the metering of fluids to or from a plurality of flow passages. n The present application is acontinuation-inpart' of our copending application Serial No. 734,840, led March 14, 1947.

v In our aforesaid parent application we have disclosed methods and devices for maintaining a predetermined flow ratio of iiuid such as liquid fuel from a common source to a plurality of outlets, or from a plurality of sources to a common outlet, irrespective of differences in discharge pressures of the outlets lor sources or variations in iiuid flow rates. We pointed out therein how theinvention finds utility in the control of fuel distribution in gas turbine engines, or for regulating flow from a plurality of fuel tanks.

According to certain embodiments of the invention, as disclosed in the parent application, a plurality of individual flow passages are controlled to maintain a predetermined flow ratio to a pilot passage and flow through the pilot passage is modified in response to major pressure variations in any of the controlled passages by a throttle Valve that communicates not only with pressure head in the controlled passages but also with the pressure head between fixed orifices in the pilot passage.

We now find that improved results are attained by having the pilot modifying communication between only the throttle valve of the pilot passage and the controlled or slave passages. Further improvement accrues also from having the pilot passage more positively adjustable by control valve means sensitively responsirve through a one way check valved reference system'to pressure variations in any of the slave passages. Such pressure variation adjustment of vthe pilot control Valve means results in either an increase or decrease, as the case may be, in the pressure head between xed orifices in the pilot passage, and thus by direct reference to control valves in the slave passages in immediate corresponding pressure adjustment in the slave passages.

An object of the present invention is to provide a fluid control system which will maintain predetermined practically perfect distribution of fluid from a single: source or stream to a plurality` ofoutlets or from a plurality of sources to a single stream or outlet irrespective of various conditions encountered in the system, such as uneven discharge pressures or variations in fluid flow rates.

sec. 266) Another object of the invention is to provide in a fluid control system for a plurality of individual streams operating in parallel, a control upon the flow in all of the streams based upon the flow through a pilot stream, and in addition, control in a novel manner of the pilot stream to correlate the same with variable conditions that may prevail in any of the streams under the control of the pilot stream.

A further object of the present invention is to provide improved control of a system of flow passages including a throttle valved pilot passage by subjecting the pilot throttle valve` exclusively to substantialV variations in pressure in the pilot controlled passages and relying upon pressure modifications thereby effected in the pilot passage to, effect appropriate uniform alteration in the now rate of the remaining passages.

It is also an object of the present invention to provide improvements in the control of a plurality of fluid passages by subjecting a pilot passage to pressure modification by subjecting it to substantial increases or decreases in pressure in any of the passages controlled thereby.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain preferred embodiments thereof, taken in conjunction with the accompanying one sheet of drawings, in which:

Figure l is aschematic fragmental sectional view illustrating a system for equally or proportionally distributing fluid, such as liquid fuel to and through.I a plurality of flow passages or ducts; and

Figure 2 is a schematic fragmental sectional view of a system similar to that shown in Figure 1 but arranged for proportionally or uniformly consolidating the ow through and from a plurality of streams such as may leadY from individual fuel tanks of an air borne machine, or the like.

In both figures of the drawings the intermediate horizontal break denotes the omission of one or more uid passage sections or assemblies.

. In Figure 1 is shown an apparatus I0 in which liquid derived from any one or more sources under pressureV is delivered to a plurality of passageways for conducting individual streams of the liquid in parallel to individual outlets or orifices (not shown) such as jet nozzles delivering to the combustion chamber of a gas turbine engine and wherein it is important that the com- Y bustion chamber receives identical amounts of liquid fuel from each nozzle despite a Wide range vprovide throttle of factors which may disturb or alter the fuel flow in one of the passages serving as a pilot, or in any of the other fluid passages.

In Figure 2 is shown substantially the reverse of the system, as illustrated in Figure 1, wherein flow from a plurality of sources, such as a plurality of fuel tanks must be coordinated and proportioned or equalized so as to assure emptying the tanks at a predetermined ratio or equally, as the case may be, in an apparatus l'.

In the apparatus of Figure l, fluid from any suitable source such as a tank (not shown) and under pressure is delivered to a manifold passage I4 and from which the fluid fiows through a plurality of distributing passages I5. In each of the passages I5 the fluid must travel through a metering jet or orifice IS to a chamber I1 bounded on one side by a limp diaphragm Iii carrying a valve plug |-9 which controls flow through an orifice to a passage 2| that leads to the respective nozzle or other outlet to which the fluid is directed in the stream afforded by the described passageway The valve plug I9 has a slotted or grooved cylindrical end portion |9a adjacent to the diaphragm I8 and snugly slidable in the orifice 20 and connected through a rod portion |9b with a second cylindrical portion |9c snugly slidable in a surrounding seat or bearing 22. A passageway 23 connects the chamber with the bottom face of the cylindrical portion |9`c whereby the static fuel pressure in the chamber I1 is caused to act on the entire area of the diaphragm I8. The areas of the cylindrical portions |9a and |90 exposed to the passageway 2| are equal so that the forces resulting from static fuel pressure in the passageway 2| are balanced.

The cylindrical portion I9a has grooves or slots 24 extending longitudinally thereof at spaced intervals around its periphery, and these grooves are closed at their upper ends by a head I9d on the top of the cylindrical portion. The lower ends of the grooves communicate through the bottom of the cylindrical portion to discharge into the passageway 2|, and the grooves valve passages through the orilice 20. Thus the flow rate through the orice 20' and hence the pressure downstream from the orifice I6 is determined by the proportion of the upper end portions of the grooves 24 that is eX- posed to the chamber I1.

A. washer 25 is bottomed on the head |9d' of the plug I9 and underlies the central portion of the diaphragm I8. A second washer 26 overlies the diaphragm I8, and a nut 21 threaded on the upper end |9e of the plug clamps the washers 25 and 26 on the diaphragm and anchors the plug valve tothe diaphragm. n

' A chamber 29 is provided above each diaphragm I8 and is separated from the chamber by the diaphragm.

One of the fluid conducting branches that leads from the manifold passage I4 is utilized as a pilot, such pilot branch passage being identified at and containing a pilot orifice 3| which discharges into a chamber 90 whence the fluid must pass through a jet or orice 9| into a chamber 92' communicating through a passage 93 with a nozzle or other outlet (not shown) which may be the same as the discharge or outlet for the respective passages 2|. The chamber 92 has thereacross a limp diaphragm 94 carrying a shutoff valve 95 adapted to coact with a seat 96 in the entrance or mouth to the passage 93. Thereby a chamber SII` is provided above the diaphragm as seen in Figure 1. The chamber 99 between the jets 3| and 9| has a static fluid pressure normally greater than prevails in the chamber 92 or the passage 93, as determined by the size of the jet 9|, and is connected through a passaged duct or conduit 98 with each of the chambers 29.

In the operation of the apparatus as thus far described, the static fuel pressure in each of the chambers 29 is at all times substantially equal to the static fuel pressure in the chamber 90. Hence, variations in fluid pressure in the passage 93- and which variations in uid pressure in the passage, are always reflected in corresponding variations in the pressure in the chamber 9D and by way of the passage 98 as variations in the static pressure in the chambers 29 and which affect the position of the respective diaphragms I8, decreases in pressure permitting the diaphragms I8 to move into the respective chambers 29 and thus permitting the fluid pressure in the respective chambers I1 to act on the diaphragme to open the valves I9 correspondingly. On the othery hand, increases in pressure in the chambers 29 act on the respective diaphragms I8 to force the same in opposition to fluid pressure in the chambers I'I, tending to close the valves I9 and thus` restrict flow to the respective passages 2 I.

Any chance in resistance to iiuid iiow in any 0f the discharge passages 2| will be transmitted back as a change in pressure in the respective chamber Ii which feeds the passage 2| thus af fected. This change in pressure causes the daphragm I8 associated with such passage 2| t0 alter the position of the plug valve I9, thus Varying the free area through the slots 24 thereof until the pressure balance between the chamber and the chamber 90 is restored. The static pressures on the downstream side of each metering `iet or orifice I6 is therefore maintained equal. Since the manifold passage I4 is relatively large, the effect of fluid friction is negligible and all 0f the branch metering orifices |6 receive the fuel at the same static pressure. The static pressure drops across the metering jets or orifices I6 are therefor maintained equal, independently of dif@ ferences in resistance to fluid flow in any of the passages 2 I.

When it is desired to maintain equal rates of flow in each of the passages 2|, as in the application of this system to a multi-jet gas-turbine engine, the branch metering orifices I6 are provided with equal orifice apertures. In other apDlCations where it may be desired to maintain a denite ratio, otherV than unity, between the rates 0f flow in the passages 2|, it is practicable to do s0 by using branch metering jets or orifices I6 Which have openings therethrough sized for giving the desired flow ratio.

According to the present invention, not only are the branch passages 2| influenced and main tained in predetermined ratio or unity of fluid flow with the pilot passage 93, but consequential variations in pressure in the respective passages 2| are reflected at all times in control of all of the other companion passages 2| and' the pilot passage 93 to vary the pressures therein correspondingly. This is true of both increases or decreases in pressure in the streams in the respective passages 2I. Herein this is accomplished by havingi the static pressure chamber 9T in check valvedA communication with each of the passages 2| by way of a duct 99. A branch duct 200 leads from each of the respective passages 2l to the duct passage 99. In control of communication between each of the branches 290 and the duct SSL 52s. isa respective check valve20| which comprises a' limp. diaphragm V202 which may conveniently be an' extension of the respective limp diaphragm I8 across a chamber 203 in eachinstance. .The check valve diaphragm 202 is disposed medially between 5 and.engageable .with equal, facility with spaced, opposed valve seats 204 and 205 extending` into, the chamber 203. The valveseats 204 are situated at the mouths of the. ducts 290, and the Valve seats 205 aiordcommunication for the end DDrtions .of the duct 99 which Ylead from or to the4 chamber203 except with respect tothe uppermost'valve seat 205 as seen at the top. of Figure l. and throughwhich communicates the duct 2.00-

from the uppermost passage 2|. .In each instance, 15

ahy-pass passageY 206 connects each side o f the limp diaphragm 202 inthe chamber 203. l.The diaphragm Y202 seeks `the seat204 or 2.0.5.I which offers the lower pressure, remaining inert when the pressures are equal or substantially,

equal.,v Thus, should there be a consequential ,presel sure increase in. one ofthe passages 2|, Athe associated diaphragm valve 202 moves awayA from the. seat 204 of the `duct 200 leading from such passage 2| andseeks the opposite seat 205, thereby 25 transmitting the increased pressure from the affected passage 2| by way of the duct v99 to the pilot chamber 91. vThis drivesthe diaphragm 913 with the valve 95 intol restricting relation to its.

seat 96 whereby to throttle ow through the pilot 30 passage v93 and develop a back pressure which is reflected inthe chamber 90. The increased Dressure istransmitted through the duct 98 tothe static, ,throttle valve pressure chambers 29 for effecting a throttled flow condition in each ofthe 3;,

passages 2| lcorresponding to the diminished uid flow prevailing in the passage 2| in which the pressure variation originated.

lBy the present'arrangement, the pressure increase in any of the passages 2| is reflected only 4o inthe chamber 91 of the pilot control stream throttle valve. assembly and not in any of the other branch streams 2| since the respective check valves 20|l associated with such other stream passages 2| will block the ducts 200 lead- 45 ing therefromv where such passages intervene bef tween the pilot passage 93 and the passage 2| in which the variation occurs, and thercheck valve. 20|; associated'with the affected stream 2| pre-,-

vents transmission of the pressure to any passage 2|`therebeyond- For example, tracing -the effect of an increase vin pressure in the passage 2| at theV remotest passage 2| at the topvof'Figure 1, the` increased pressure is reflected through the `terminal portion of the duct 99 leading from the up- 55.

per passage 2|, drivesY the diaphragm 202 of the associated check valve 20| against the seat 204 atv themouth of the branch passage 200 of the next-succeeding branch 2| and then travels by Way-of the respective by-pass passage 206 onward 00 through the duct 99, repeating the performance at each of the check valves 20| until the pressure reaches the chamber 91. In any instance, even thoughv there should be a pressure increase in one off the succeeding passages 2| simultaneously65 witha greater increase in a preceding passage 2| (compare the topmost passage 2|I with the third branch from the top of Figure l)l the greater pressurewill be passed on to the chamber 91 .and

all of tthe'passages 2| and 93 thus brought under 70 thecontrol-variation initiated by the greater pressure.v- Should the increased-pressure origi.

nate in any of the intermediate passages 2|, thediaphragm valve 2024 associated with -the check vali/61:20lr-companion to` such--intermediate-pas 75 ams-,eea

sage will move from the full line position indi cated in Figure 1 to the dash line position, thus blocking travel of the pressure to the passages-2|' more remote from the pilot passage 93 but directing the pressure in one direction to the pilot chamber 91. Thus, the highest pressure in any 0f the passages 2| is transmitted positively in one direction only to the pilot chamber 91 so that the.

pilot at all times maintains control of the system;

It may also be noted that in the event of a reductionin pressure in the passage 2| that previously was at a higher pressure thanv any other passage 2| to a pressure below that existing in another lpassage 2|, such pressure reductionwill be reflected in a control response in theA system. for maintaining the equality of flow or prede-- terrnined flow ratio of the system. Thus,'in thel event of any such pressure drop, there is a pressure bleed from the pilot chamber 91 by way of the duct 99 to the affected passage 2|, whichv causes further opening of the pilot Valve 95 'by` deflection of the diaphragm 94 into the' chamber 91, and thus adrop in pressure in the chamber` which is promptly reflected in each of thev throttle valve static pressure chambers V29.

In the event that .the pressure in the passage,` 93 is higher than the pressure in any passage 2 the lpilot valve 95 moves to wide-open, thereby still maintaining the pressure in the chamber 92 equal tothe highest pressure existing at any ofA the discharge points o f the system.

It will thus be apparent that at all Vtimes not only are the several passages 2| maintained under individual pressure responsive throttle contro1, but they are maintained under pilot pressure control, and also under mutual pressure variation(- contro1, the latter being, of course, reflected through the pilot control.

Having reference now to the Aform of Figure-2 wherein equality of ow or predetermined ow' ratio is maintained from a plurality of passages 62 leading from separate fluid sources such as fuel tanks in an air borne machine such as an airplane or the like, are arranged in parallel with" a pilot passage 65 which may also lead from* a similar individual fluid source. The arrangement` is such that the flow through each of the passages 62 is maintained equal or in ypredetermined'A ratio to the ow through the. passage 65, and also variations in the fluid pressure in any ofthe pas-1 sages 62 are effective to adjust the pressures in'a'll of the other flow passages.

The-pilot passage 65 has a, nedpilot regulator; jet or orifice 66 discharging into a chamber 01v of the apparatus I0', and fluid passes from the chamber61 through a pilot metering v-jet or ori# ce Binto a branch passage 69 emptying"intoa;v

manifold passage 10.

Each of the passages 62 is controlled bya throti' tle valveV 1| for discharge into a chamber -12 which. communicates by way of a passage 12a withfaf pressure chamber 13. From the chamber 1 3 iiuid.

passes by way of a metering jet o r orifice 14 linto aibranchpassageway 15 that leads into the manifold passage 10.

aces-,oas

amounts determined by the extent of exposure of the ends of the slots to the passage or .chamber 12.V The valves 1I are balanced in the same manner as the valves I9, described in connection with Figure l. That is, the pressure of iluid upstream from the respective orice 14 is reflectedv stream in the passage 65 or by suction in the manifold 10, being immaterial, flows through the jet or vorifice 66 into thechamber 61 and the metering jet or orifice 68 and develops fluid pressure in the chamber 61. This pressure in the chamber 61 is transmitted through the 'passage BI to each of the throttle chambers 60. The pressure in the chambers 80 acts on'th'e diaphragme 16 to open the throttle valves 1I, but this action is resisted by the pressure in the chambers 13 on the other sides of the diaphragms. The pressure in each chamber 13 will change Whenever the pressure drop across the branch metering jet or oriiice 14 changes. Since each of the branch metering iets 14 discharges into the same .manifold :passage as the pilot metering jet or orifice 68, which maintains pressure in the chamber 61., it is evident that any variation in the pressure drop across the pilot regulator jetor oriceG will immediately be reflected vin a pressure change in the chambers 80, thereby changing the setting or position of the respective throttle valves 1I and maintaining a constant ilow ratio in the passages-62 and 65. If the sizes of the metering oriiices are equal, the flow rate in each passage will be identical as determined by the pilot passage 65. The system of Figure 2, therefore, operates substantially in reverse relation to the system of Figure l.

In addition to control of the system responsive to variations in the pilot stream of the passage 65, means are provided for mutual responsiveness of the several passages 62 to variations occurring in any of the passages, as reflected through controlv of the pilot stream. To this end, the pilot passage 65- is equipped with a throttle valve IIO controlled by a limp diaphragm III between a chamber II2 and a chamber II3. The chamber II3 is connected by a duct passageway .I I4 with all of the fluid passages 62.

The pilot throttle valve I I0 is preferably similar to the passage throttle valves 1I, and includes a longitudinally slotted metering plug portion I I1 which is slidable in an orifice I I8 whence the metered fluid enters a passage chamber 119 and escapes by way of a passage to the throttle valve chamber I I2 for influencing the diaphragm I II and thus the action of the throttle valve I I0.

` By having the pilot throttle valve chamber I I3 communicating with the passages 62, the lowest pressure in any of the passages 62 will be renected in the pilot stream to' control anni the passages.

ln order' to assure that the lowest pressure in the passages 62 will be transmitted in one direction only to the chamber I'I3, check valves 300 are interposed at the juncture of the duct H4 and respective branch passages leading from the passages 62 to the duct I I4.

In the" present instance `each of the' check valves 300 kcomprises a spool type member 302.

carrying valve 'heads 303 and 304 at its respective opposite ends. Valve seats 305 and 306 for the valve heads 303 and 304, respectively, are disposed at opposite ends of a cross duct 301 into Which the duct I I4 opens between the valve heads 303 and 304.

Normally the check valve member 302 will move away from the greater pressure to block escape of the pressure past the respective valve seat 305 or 306 to the duct II4 and lthus eventually to the throttle static pressure chamber II3- As a result, only low pressure exposure of the chamber Il3 will prevail. pressure in any of the passages 62 will bereflected in the throttle chamber II3, causing the diaphragm III to move into the chamber II3 and throttle flow through the pilot passage 65. causing a drop in pressure in the chamber 61 and corresponding drop in all of. the throttle valve chambers and thus return the system to beflance orthe predetermined ratio for which it may be adjusted.

By way. of illustration in Figure 2, the check valve 300 associated with the passage 62 nearest the throttle passage 65 is shown as displaced to close the valve seat 306 because the pressure has dropped in a passage 62 more remote from the pilot-passage 65 so that the greater pressure in the adjacent passage 62 acting on the associated check valve 300 causes the check valve member 302 to be moved under the iniluence of the greater pressure to block escape of the'pressure while at the same time opening the controlled sectionv of the duct II4 for exposure through the duct II4 of the chamber I I3 to the pressure drop from4 the low pressure passage 62.

In the event that the pressure in the passage 65 is lower than the pressure existing in any passage 62, the throttle valve IIO moves to wideopen, thereby still maintaining the pressure in the chamber II2 equal to the lowest pressure existing in -any of the source points of the system.

From the foregoing it will be apparent that the present invention provides a highly advantageous method and apparatus for controlling the ow of a plurality of parallel streams, where the streams are al1 ilowing to different discharge points or where the streams all originate Yat dif-- ferent sources .and flow to a common discharge point or to separate discharge points. Not only are the streams individually throttled for uniformity `of ow therethrough but they are co1- lectively controlled by a pilot stream, and are mutually responsible for controlling the iiowsystem as reiiected through the pilot. The invention therefore aords a highly sensitive control' for plural streams and which control is responsive to a great variety of conditions throughout the system andwithin a wide range of variable factors.

It will, of course, be understood that various details in the present disclosure may be variedl through .a wide range Without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by thescope of the appended claims.

The invention described herein may be manuj factured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties.

thereon or therefor.

We claim as our invention:

Hence, the' lowest vthe flow of fluid through a plurality of fluidpasfr sages, pressure-sensitive means for individually -controlling each of said passages, a singlepilot passage, spaced pressure controlling orifice 'meansin said pilot passage defining therebe- "twe'en a static pressure head, means effecting communication between said static pressure head and each of the pressure-sensitive control means for said plurality of passages for coordinating the ilow through said plurality of passages with the ilow through said pilot passage, a pressure-sensitive valve for adjusting the flow ythrough said pilot passage, and means effecting communication with said pressure-sensitive valve and each of said plurality of passages to render said pressure-sensitive valve responsive to the 'greatest departure in pressure in any of sai-d plurality of passages from the relative pressure con- 'dition established in said plurality of passages as a result of said coordinating of flow therein with flow through said pilot passage. n

2. In apparatus of the character described, a plurality of separate fluid flow slave. passages, an orifice in each of said passages, means defining a chamber in each of said passages, a separate throttle valve in and controlling ilow through each of said passages, each of said valves having a limp diaphragm operator dividing the chamber in the associated passage into a dynamic pressure portion and a static pressure portion, the passages having portions thereof communicating in fluid flow relation with said dynamic pressure portions of the respective chambers so that the pressure of the fluid flowing through the respective passages is effective inthe dynamic pressure portions of the chambers to operate the respective diaphragm for controlling the associated throttle valves, a pilot passage having two orifices therein in series vdefining a pressure head area therebetween, fluid duct means effecting vcommunication of said pressure head area with the static pressure portions of said-chambers, a throttle valve in control of the pilot passage, pressure-responsive means for actuating said pilot passage throttle valve, and means for selectively` effecting communication between said 'pressure responsive means and that one of said slave passages in which the pressure has departedthe greatest amount in a predetermined directionV from a pressure as determined by the communication of said pressure head area with the static pressure portions of said vchambers whereby to adjust/thev pilot passage throttle valve and thereby adjust the pressure in said pressure head area for corespondingly adjusting all of the remaining slave passages substantially conformable to said one slave passage.

f3. In 'apparatus for controlling the ilow of fluid through a plurality of passages to maintain a predetermined kflovv ratio in said j passages, one of said passages serving as a pilot and having a pair of restricted orifices therein affording a pressure head therebetween, s the remaining passages being in slave relation to said pilot passage and each having a metering orifice therein determinative-o-f the fluid ilowk through the passage, each of said slave passages having a separate throttle valve therein spaced from. the metering orifice in fsuch slave passage for controlling pressure fluctuations therein and each of said throttle valves including a diaphragrn actuator exposed on one side tothe dynamic pressure of fluid within the associated passage'and having'a static pressure area on the freres@ 'otiiersiueiof the diaphra'gm`-actuator, the l"static pressure areas of all of said throttle valve actuators being in pressure communication with said pressure head for coordinating thehopera-tion of the throttle valves and thereby the flow through 'said slave passages responsiveto"variations Ain 'said pressure head, said pilot passage having a diaphragm-controlled throttle valve therein one side of which is responisve to the dynamic pressure of fluid flowing through the pilot passage `and the other side of which is exposed to a static pressure chamber, and means having communication with only said static pressure chamber insofar as the pilot passage is concerned and with each of said slave passages for rendering said static pressure chamber sensitive to-'the pressure condition in that slave passage vwhich has departedthe greatest amount in a predetermined direction from the coordinated flow condition established said slave passages as aforesaid, whereby to effect adjustmentv of said pilot passage throttle valvey and thus condition the pressure in said pressure head for correspondingly effecting readjustment of' allof the throttle valves in the remaining slave passages.

4.111 apparatus for controlling the flow-fof fluid through a plurality of passages to maintain a predetermined flow ratio in said passages, one of said passages serving asa pilot and having a pair of restricted oriflcestherein affording a pressure head therebetween, vthe remaining passages being in slaverelation to said pilot passage Aand each having a metering orifice therein determinative of the iluid ilow' through the passage, each of said slave passages having a separate throttle valve .therein spaced-fromthe metering orifice in such slave passage for controlling pressure lluctuations therein and each of said throttle valves including a diaphragm actuator exposedon one side to the dynamic pressure of fluid within the associated passage and having a static pressure area on the otherside of the diaphragm actuator, the Vstatic pressure areas of all of said throttle valve actuators being in pressure communication with said pressure head for/coordinating the operation of the throttle valves and thereby the flow' through said slave Kpassages responsive to variations in said pressure head, said pilot passage having a diaphragm-'controlled throttle valve therein^one side of which is responsive to the dynamic pressure of fluid flowing through the pilot passage and the other sideof which is exposed to a'static pressure chamber, and means having communication with only said static pressure chamber insofar as the pilot passage is concerned and with each of said slave passages for rendering said static pressure chamber sensitive to the pressure condition in that slave passage which has departed thev greatest amount in a predetermined direction from the coordinatedv 'flow' condition established in` said slave passagesy as aforesaid, whereby to effect adjustment of said pilot passage throttle valve and thus condition the pressure inV said pressure head for vcorrespondingly effecting readjustment `of all o f the throttle valves in the remaining slave passages', said communication means including a passage leading to said `pilot static pressure chamber and with a branch leading to' said communicationrmeans passage from each of said slave passages and having a valve in control ofA each branch. p Y

5. In combination in control apparatus for maintaining a predetermined fluid flow ratio in pressure-sensitive checkV a plurality of uid passages vwherein there. ls concurrent uid i'low created by differential line pressure in theseveral passages, one of said passages serving as a pilot andthe remaining passages being Vin slave relation to the pilot passage, respective pressure responsive means, for individually controlling the passages, means comprising a duct leading from the pilot passage at one side of the control means therein and operatively communicating with said control means in the slave passages for adjustably actuating the latter responsive vto pressure variations in the pilot passage for thereby maintaining substantially a predetermined flow ratio in the slave passages relative to the pilot passage, and meansincluding a duct communicating at one terminus with the pilot passage controlling means and having respective branch ducts leading thereto from said slave passages, said communicating duct having respective check valve means at said branch ducts operatively responsive `to predetermined pressure differential in onev of said slave passages relative to the other slave passages for selectively effecting communication through said communicating duct with the pilot passage controlling means for adjusting the latter to modify the pilot passage pressure and thereby effecting adjustment of the slave passage controlling means through said duct leading to said slave passage controlling means.

6. Apparatus as defined inV claim 5, wherein said check valve means comprise limp diaphrag-ms which remain inactive during the predetermined fluid now ratio conditions in said passages but act under excess pressure in the respecu tively associated slave passage to block backsurge of excess pressure through said communicating duct and limiting excess pressure flow through said communicating duct toward said terminus.

'7. Apparatus as deiined in claim 5 wherein said check valves comprise spool-type members which remain inactive during predetermined fluid flow ratio conditions in said slave passages, but act respectively under deficient pressure in said communicating duct originating from the respectively associated slave passage to block escape of pressure through the communicating duct away from said terminus but limiting reference of said deficient pressure toward said` terminus for corresponding adjustment of the pilot valvel controlling means.

8. In a multi-passage iluid control system wherein a predetermined fluid flow ratio must be maintained in allyof the passages irrespective of variation in flow rate, and whereinea-ch of the passages communicates at its opposite ends with respective pressure regions in differential pressure relationship `and each passage` containsv respective means for individually controlling flow therethrough to maintain a predetermined relative flow ratio in the passages, one of the passages serving as a pilot and having a pair of spaced orices therein developing a pressure head zone therebetween which is connected through duct means with the control means of each Yof the remaining passages which are thus placed in slave relation to the pilot passage; the improvement which comprises the pilot passage control means being a pressure-sensitive throttle valve, and a duct having a terminus connected with said throttle valve and communicating with each of the slave passages, said duct having at each of the slave passages afrespective'check valve structure. comprising in each instance a balanced dial2 phragnr andv opposed val-ve seats selectively engageable by the diaphragm, one of said seats in each instance communicating vv'iththe4 associated slave passage and the other of saidrseats being disposed directly inthe adjacent portiono the flow passage in said.4 duct, whereby upon the development of a fluid pressure in any of said slave passages inexcess of pressure determined by said pilot passagecontrol` of said slave passages will drive the-diaphragmassociated with said one passageagainst the associated valve seat in the `duct to direct pressure referenced throughvthe duct Y toward. said terminus, the diaphragms of the check. valve structuresrv of slave passages communicating with said ductintermediate-saidfone slave passage and said' terminus being driven. by said excess pressure against the respectively associated passagefcommunicating valve seats to block direct reflection of'said excess'pressure in said intermediate slave passages.

9. In apparatus including a plurality of. uid passages,l one of said passages serving as a pilot for maintaining the other passages in :slave rela: tion to said pilot passage, each of the passages in cluding a pressure-responsive throttle valve therein for controlling flo-w therethrough, means for controllingV the slave passages respective to pressure iiuctuations in the pilot passage comprising a duct connecting a portion of thepilot passage with each of said pressure-responsive throttle valves in the slave passages, andv mean for controlling flow through the pilot passage responsive to pressure fluctuation in any one of said slave passages causing departure from a predetermined fluid flow ratio, comprising a duct communicating with each of said slave passages but with respect to the pilot passage communicating solely with the throttle valve therein for adjustment of the pilot throttle valve in accordance with the pressure departure in said one slave passage to thereby conform the throttle pilot passage pressure to said departure and thus effect readjustrnent of the slave passage controlling throttle valve to return the passages to a prede.- termined fluid flow ratio under the control of the pilot passage.

10. In a now control system for maintaining proportional owthrough aplurality of slave passages wherein one of said slave passages. communicates at its opposite ends with respectively first and second pressure regions in. differential pressure relation to eifect fluid flow .in one direction between said pressure regions for all of said passages, said slave passages having therein. re.- spective metering orifice means, all of said orice means on one sidebeing subjected to thev pressure conditions prevailing in the rst pressure region; pressure loaded pressure control means ineach4 slave passage on the other side of said orifice means therein arranged to control the pressure at the other side of such oriflcemeans in accordance with the loading pressure; means forl applyestablishing communication between said zonev and each of said pressure control means; the

pressure in said zone in accordance with the prespassages, sure in any slave passage in which the pressure HAROLD GOLD. ,f control means is caused by line pressure factors 5 DAVID M. STRAIGHT. in such slave passage to depart in a predeterminedddiretctiont from aid commonblloadintgp'ies' References Cited in the file of this patent sure a jus men comprising varia e res r c on I means in said pilot passage between said zone and UNITED STATES PATENTS the other end of said pilot passage and including 10 Number Name Date a pressure actuator, interconnecting conduit 1,452,265 Collins Apr. 17, 1923 means connecting each of said slave passages on 1,590,275 Bayless June 29, 1926 the other side of its metering orifice means with 2,313,797 Bailey Mar. 16, 1943 the pressure actuator, and respective check valve 2,430,264 Wiegand et a1. Nov. 4, 1947 means associated With said interconnecting con- 15 2,606,066 Thompson Aug. 5, 1952 duit means and being operable to open selectively 2,621,719 Eaton et a1 Dec. 16, 1952 communication between the pressure actuator Y and the slave passage in which the pressure de- Y .FGREIGN PATENTS parts in said predetermined direction from the Y Number Countryy Date common loading pressure adjustment, to sub- 20 577,132 Great Britain of 1946 combination with said pressure control means said zone and thus eiect corresponding readj ustand said pressure zone of means for varying the ment of the loading pressures in all of the slave stantially proportionally readjust the pressure in 526,869 Germany of 1931 

